Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

34 files changed, 1703 insertions, 0 deletions

diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/browser.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/browser.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/absent-value-not-passed.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/absent-value-not-passed.js
new file mode 100644
index 0000000000..ecba51e39c
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/absent-value-not-passed.js
@@ -0,0 +1,38 @@
+// |reftest| async
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: >
+  `next` method does not pass absent `value`.
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+
+  [...]
+  5. If value is present, then
+    [...]
+  6. Else,
+    a. Let result be IteratorNext(syncIteratorRecord).
+  [...]
+flags: [async]
+features: [async-iteration]
+includes: [asyncHelpers.js]
+---*/
+
+var nextArgumentsLength;
+var syncIterator = {
+  [Symbol.iterator]() {
+    return this;
+  },
+  next() {
+    nextArgumentsLength = arguments.length;
+    return {done: true};
+  },
+};
+
+asyncTest(async function () {
+  for await (let _ of syncIterator);
+
+  assert.sameValue(nextArgumentsLength, 0);
+});
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/browser.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/browser.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-done.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-done.js
new file mode 100644
index 0000000000..eb493bece9
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-done.js
@@ -0,0 +1,53 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: next() will reject promise if getter `done` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let nextResult be IteratorNext(syncIteratorRecord, value).
+  6. IfAbruptRejectPromise(nextResult, promiseCapability).
+  7. Let nextDone be IteratorComplete(nextResult).
+  8. IfAbruptRejectPromise(nextDone, promiseCapability).
+  ...
+  18. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return {
+          get done() {
+            throw thrownError;
+          },
+          value: 1
+        }
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+asyncg().next().then(
+  function (result) {
+    throw new Test262Error("Promise should be rejected.");
+  },
+  function (err) {
+    assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+  }
+).then($DONE, $DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-value.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-value.js
new file mode 100644
index 0000000000..6a0e49439d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-poisoned-value.js
@@ -0,0 +1,55 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: next() will reject promise if getter `value` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let nextResult be IteratorNext(syncIteratorRecord, value).
+  6. IfAbruptRejectPromise(nextResult, promiseCapability).
+  7. Let nextDone be IteratorComplete(nextResult).
+  8. If AbruptRejectPromise(nextDone, promiseCapability).
+  9. Let nextValue be IteratorValue(nextResult).
+  10. IfAbruptRejectPromise(nextValue, promiseCapability).
+  ...
+  18. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return {
+          get value() {
+            throw thrownError;
+          },
+          done: false
+        }
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+asyncg().next().then(
+  function (result) {
+    throw new Test262Error("Promise should be rejected.");
+  },
+  function (err) {
+    assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+  }
+).then($DONE, $DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-prototype.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-prototype.js
new file mode 100644
index 0000000000..d3f638e48e
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-prototype.js
@@ -0,0 +1,43 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: next() returns a promise for an IteratorResult object
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let nextResult be IteratorNext(syncIteratorRecord, value).
+  6. IfAbruptRejectPromise(nextResult, promiseCapability).
+  7. Let nextDone be IteratorComplete(nextResult).
+  8. If AbruptRejectPromise(nextDone, promiseCapability).
+  9. Let nextValue be IteratorValue(nextResult).
+  10. IfAbruptRejectPromise(nextValue, promiseCapability).
+  ...
+  14. Let steps be the algorithm steps defined in Async-from-Sync Iterator Value Unwrap Functions.
+
+  Async-from-Sync Iterator Value Unwrap Functions
+  1. Return ! CreateIterResultObject(value, F.[[Done]]).
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+function* g() {}
+
+async function* asyncg() {
+  yield* g();
+}
+
+asyncg().next().then(function (result) {
+  assert(
+    Object.prototype.hasOwnProperty.call(result, 'value'), 'Has "own" property `value`'
+  );
+  assert(
+    Object.prototype.hasOwnProperty.call(result, 'done'), 'Has "own" property `done`'
+  );
+  assert.sameValue(Object.getPrototypeOf(result), Object.prototype);
+}).then($DONE, $DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-rejected.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-rejected.js
new file mode 100644
index 0000000000..8a5f9bf14a
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-rejected.js
@@ -0,0 +1,44 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: next() will reject promise if sync iterator next() function returns an aburpt completion
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let nextResult be IteratorNext(syncIteratorRecord, value).
+  6. IfAbruptRejectPromise(nextResult, promiseCapability).
+  7. Let nextDone be IteratorComplete(nextResult).
+  8. If AbruptRejectPromise(nextDone, promiseCapability).
+  9. Let nextValue be IteratorValue(nextResult).
+  10. IfAbruptRejectPromise(nextValue, promiseCapability).
+  ...
+  18. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+function* g() {
+  throw thrownError;
+}
+
+async function* asyncg() {
+  yield* g();
+}
+
+asyncg().next().then(
+  function (result) {
+    throw new Test262Error("Promise should be rejected.");
+  },
+  function (err) {
+    assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+  }
+).then($DONE, $DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-unwrap-promise.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-unwrap-promise.js
new file mode 100644
index 0000000000..f77f3c2d96
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/iterator-result-unwrap-promise.js
@@ -0,0 +1,44 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: next() will unwrap a Promise value return by the sync iterator
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let nextResult be IteratorNext(syncIteratorRecord, value).
+  6. IfAbruptRejectPromise(nextResult, promiseCapability).
+  7. Let nextDone be IteratorComplete(nextResult).
+  8. If AbruptRejectPromise(nextDone, promiseCapability).
+  9. Let nextValue be IteratorValue(nextResult).
+  10. IfAbruptRejectPromise(nextValue, promiseCapability).
+  ...
+  14. Let steps be the algorithm steps defined in Async-from-Sync Iterator Value Unwrap Functions.
+
+  Async-from-Sync Iterator Value Unwrap Functions
+  An async-from-sync iterator value unwrap function is an anonymous built-in
+  function that is used by methods of %AsyncFromSyncIteratorPrototype% when
+  processing the value field of an IteratorResult object, in order to wait for
+  its value if it is a promise and re-package the result in a new "unwrapped"
+  IteratorResult object. Each async iterator value unwrap function has a
+  [[Done]] internal slot.
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+function* g() {
+  yield Promise.resolve(1);
+}
+
+async function* asyncg() {
+  yield* g();
+}
+
+asyncg().next().then(function (result) {
+  assert.sameValue(result.value, 1, "result.value should be unwrapped promise, got: " + result.value)
+}).then($DONE, $DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/return-promise.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/return-promise.js
new file mode 100644
index 0000000000..4f6a112c45
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/return-promise.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.next
+description: >
+  "next" returns a promise for an IteratorResult object
+info: |
+  %AsyncFromSyncIteratorPrototype%.next ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  18. Return promiseCapability.[[Promise]].
+
+features: [async-iteration]
+---*/
+
+function* g() {
+}
+
+async function* asyncg() {
+  yield* g();
+}
+
+var result = asyncg().next();
+assert(result instanceof Promise)
+
+reportCompare(0, 0);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/shell.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/shell.js
new file mode 100644
index 0000000000..ae18ad584d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/next/shell.js
@@ -0,0 +1,113 @@
+// GENERATED, DO NOT EDIT
+// file: asyncHelpers.js
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+description: |
+    A collection of assertion and wrapper functions for testing asynchronous built-ins.
+defines: [asyncTest]
+---*/
+
+function asyncTest(testFunc) {
+  if (!Object.hasOwn(globalThis, "$DONE")) {
+    throw new Test262Error("asyncTest called without async flag");
+  }
+  if (typeof testFunc !== "function") {
+    $DONE(new Test262Error("asyncTest called with non-function argument"));
+    return;
+  }
+  try {
+    testFunc().then(
+      function () {
+        $DONE();
+      },
+      function (error) {
+        $DONE(error);
+      }
+    );
+  } catch (syncError) {
+    $DONE(syncError);
+  }
+}
+
+assert.throwsAsync = async function (expectedErrorConstructor, func, message) {
+  var innerThenable;
+  if (message === undefined) {
+    message = "";
+  } else {
+    message += " ";
+  }
+  if (typeof func === "function") {
+    try {
+      innerThenable = func();
+      if (
+        innerThenable === null ||
+        typeof innerThenable !== "object" ||
+        typeof innerThenable.then !== "function"
+      ) {
+        message +=
+          "Expected to obtain an inner promise that would reject with a" +
+          expectedErrorConstructor.name +
+          " but result was not a thenable";
+        throw new Test262Error(message);
+      }
+    } catch (thrown) {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but an exception was thrown synchronously while obtaining the inner promise";
+      throw new Test262Error(message);
+    }
+  } else {
+    message +=
+      "assert.throwsAsync called with an argument that is not a function";
+    throw new Test262Error(message);
+  }
+
+  try {
+    return innerThenable.then(
+      function () {
+        message +=
+          "Expected a " +
+          expectedErrorConstructor.name +
+          " to be thrown asynchronously but no exception was thrown at all";
+        throw new Test262Error(message);
+      },
+      function (thrown) {
+        var expectedName, actualName;
+        if (typeof thrown !== "object" || thrown === null) {
+          message += "Thrown value was not an object!";
+          throw new Test262Error(message);
+        } else if (thrown.constructor !== expectedErrorConstructor) {
+          expectedName = expectedErrorConstructor.name;
+          actualName = thrown.constructor.name;
+          if (expectedName === actualName) {
+            message +=
+              "Expected a " +
+              expectedName +
+              " but got a different error constructor with the same name";
+          } else {
+            message +=
+              "Expected a " + expectedName + " but got a " + actualName;
+          }
+          throw new Test262Error(message);
+        }
+      }
+    );
+  } catch (thrown) {
+    if (typeof thrown !== "object" || thrown === null) {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but innerThenable synchronously threw a value that was not an object ";
+    } else {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but a " +
+        thrown.constructor.name +
+        " was thrown synchronously";
+    }
+    throw new Test262Error(message);
+  }
+};
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/absent-value-not-passed.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/absent-value-not-passed.js
new file mode 100644
index 0000000000..21686a8896
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/absent-value-not-passed.js
@@ -0,0 +1,43 @@
+// |reftest| async
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: >
+  `return` method does not pass absent `value`.
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+
+  [...]
+  8. If value is present, then
+    [...]
+  9. Else,
+    a. Let result be Call(return, syncIterator).
+  [...]
+flags: [async]
+features: [async-iteration]
+includes: [asyncHelpers.js]
+---*/
+
+var returnArgumentsLength;
+var syncIterator = {
+  [Symbol.iterator]() {
+    return this;
+  },
+  next() {
+    return {done: false};
+  },
+  return() {
+    returnArgumentsLength = arguments.length;
+    return {done: true};
+  },
+};
+
+asyncTest(async function () {
+  for await (let _ of syncIterator) {
+    break;
+  }
+
+  assert.sameValue(returnArgumentsLength, 0);
+});
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/browser.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/browser.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-done.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-done.js
new file mode 100644
index 0000000000..de5639aa9d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-done.js
@@ -0,0 +1,71 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will reject promise if getter `done` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  ...
+  8. Let returnResult be Call(return, syncIterator, « value »).
+  9. IfAbruptRejectPromise(returnResult, promiseCapability).
+  ...
+  11. Let returnDone be IteratorComplete(returnResult).
+  12. IfAbruptRejectPromise(returnDone, promiseCapability).
+  13. Let returnValue be IteratorValue(returnResult).
+  14. IfAbruptRejectPromise(returnValue, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      return() {
+        return {
+          get done() {
+            throw thrownError;
+          },
+          value: 1
+        }
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-value.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-value.js
new file mode 100644
index 0000000000..369319f098
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-poisoned-value.js
@@ -0,0 +1,71 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will reject promise if getter `value` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  ...
+  8. Let returnResult be Call(return, syncIterator, « value »).
+  9. IfAbruptRejectPromise(returnResult, promiseCapability).
+  ...
+  11. Let returnDone be IteratorComplete(returnResult).
+  12. IfAbruptRejectPromise(returnDone, promiseCapability).
+  13. Let returnValue be IteratorValue(returnResult).
+  14. IfAbruptRejectPromise(returnValue, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+
+var thrownError = new Error("Catch me.");
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      return() {
+        return {
+          get value() {
+            throw thrownError;
+          },
+          done: false
+        }
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-unwrap-promise.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-unwrap-promise.js
new file mode 100644
index 0000000000..5d69a98f7f
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result-unwrap-promise.js
@@ -0,0 +1,65 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will unwrap a Promise value return by the sync iterator
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  ...
+  17. Let steps be the algorithm steps defined in Async-from-Sync Iterator Value Unwrap Functions.
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+  Async-from-Sync Iterator Value Unwrap Functions
+  An async-from-sync iterator value unwrap function is an anonymous built-in
+  function that is used by methods of %AsyncFromSyncIteratorPrototype% when
+  processing the value field of an IteratorResult object, in order to wait for
+  its value if it is a promise and re-package the result in a new "unwrapped"
+  IteratorResult object. Each async iterator value unwrap function has a
+  [[Done]] internal slot.
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      return() {
+        return {
+          value: Promise.resolve(42),
+          done: true
+        };
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+let iter = asyncg();
+
+iter.next().then(function (result) {
+  iter.return().then(
+    function (result) {
+      assert.sameValue(result.value, 42, "Result.value should be unwrapped, got: " + result.value);
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result.js
new file mode 100644
index 0000000000..38ac3eeaa5
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/iterator-result.js
@@ -0,0 +1,56 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will return a iterator result object when built-in sync throw is called
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  ...
+  8. Let returnResult be Call(return, syncIterator, « value »).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+  Generator.prototype.return ( value )
+  1. Let g be the this value.
+  2. Let C be Completion{[[Type]]: return, [[Value]]: value, [[Target]]: empty}.
+  3. Return ? GeneratorResumeAbrupt(g, C).
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+function* g() {
+  yield 42;
+  throw new Test262Error('return closes iter');
+  yield 43;
+}
+
+async function* asyncg() {
+  yield* g();
+}
+
+var iter = asyncg();
+var val = 'some specific return value'
+
+iter.next().then(function(result) {
+
+  // return will call sync generator prototype built-in function return
+  iter.return(val).then(function(result) {
+
+    assert.sameValue(result.done, true, 'the iterator is completed');
+    assert.sameValue(result.value, val, 'expect agrument to `return`');
+
+    iter.next().then(({ done, value }) => {
+      assert.sameValue(done, true, 'the iterator is completed');
+      assert.sameValue(value, undefined, 'value is undefined');
+    }).then($DONE, $DONE);
+
+  }).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-get-return.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-get-return.js
new file mode 100644
index 0000000000..c91a1954d5
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-get-return.js
@@ -0,0 +1,60 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will return rejected promise if getter of `return` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  6. IfAbruptRejectPromise(return, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      get return() {
+        throw thrownError;
+      }
+    }
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-return.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-return.js
new file mode 100644
index 0000000000..19d2be92d8
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/poisoned-return.js
@@ -0,0 +1,66 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will return rejected promise if getter of `return` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  6. IfAbruptRejectPromise(return, promiseCapability).
+  ...
+  8. Let returnResult be Call(return, syncIterator, « value »).
+  ...
+  10. If Type(returnResult) is not Object,
+    a. Perform ! Call(promiseCapability.[[Reject]], undefined, « a TypeError exception »).
+    b. Return promiseCapability.[[Promise]].
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      return() {
+        throw thrownError;
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/result-object-error.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/result-object-error.js
new file mode 100644
index 0000000000..153ff47f41
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/result-object-error.js
@@ -0,0 +1,65 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: return() will return rejected promise if getter of `return` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  6. IfAbruptRejectPromise(return, promiseCapability).
+  ...
+  8. Let returnResult be Call(return, syncIterator, « value »).
+  ...
+  10. If Type(returnResult) is not Object,
+    a. Perform ! Call(promiseCapability.[[Reject]], undefined, « a TypeError exception »).
+    b. Return promiseCapability.[[Promise]].
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      return() {
+        return 1;
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      let typeerror = err instanceof TypeError;
+      assert(typeerror, "Expect TypeError, got: " + err);
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-null.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-null.js
new file mode 100644
index 0000000000..50f94bba85
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-null.js
@@ -0,0 +1,55 @@
+// |reftest| async
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.return
+description: >
+  If syncIterator's "return" method is `null`,
+  a Promise resolved with `undefined` value is returned.
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+
+  [...]
+  5. Let return be GetMethod(syncIterator, "return").
+  [...]
+  7. If return is undefined, then
+    a. Let iterResult be ! CreateIterResultObject(value, true).
+    b. Perform ! Call(promiseCapability.[[Resolve]], undefined, « iterResult »).
+    c. Return promiseCapability.[[Promise]].
+
+  GetMethod ( V, P )
+
+  [...]
+  2. Let func be ? GetV(V, P).
+  3. If func is either undefined or null, return undefined.
+flags: [async]
+features: [async-iteration]
+includes: [asyncHelpers.js]
+---*/
+
+var iterationCount = 0;
+var returnGets = 0;
+
+var syncIterator = {
+  [Symbol.iterator]() {
+    return this;
+  },
+  next() {
+    return {value: 1, done: false};
+  },
+  get return() {
+    returnGets += 1;
+    return null;
+  },
+};
+
+asyncTest(async function() {
+  for await (let _ of syncIterator) {
+    iterationCount += 1;
+    break;
+  }
+
+  assert.sameValue(iterationCount, 1);
+  assert.sameValue(returnGets, 1);
+});
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-undefined.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-undefined.js
new file mode 100644
index 0000000000..5e5e766288
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/return-undefined.js
@@ -0,0 +1,55 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: return() will return value undefined if sync `return` is undefined
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "return").
+  6. IfAbruptRejectPromise(return, promiseCapability).
+  7. If return is undefined, then
+    a. Let iterResult be ! CreateIterResultObject(value, true).
+    b. Perform ! Call(promiseCapability.[[Resolve]], undefined, « iterResult »).
+    c. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.return().then(function(result) {
+
+    assert.sameValue(result.done, true, 'the iterator is completed');
+    assert.sameValue(result.value, undefined, 'expect value to be undefined');
+
+    iter.next().then(({ done, value }) => {
+      assert.sameValue(done, true, 'the iterator is completed');
+      assert.sameValue(value, undefined, 'value is undefined');
+    }).then($DONE, $DONE);
+
+  }).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/shell.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/shell.js
new file mode 100644
index 0000000000..ae18ad584d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/return/shell.js
@@ -0,0 +1,113 @@
+// GENERATED, DO NOT EDIT
+// file: asyncHelpers.js
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+description: |
+    A collection of assertion and wrapper functions for testing asynchronous built-ins.
+defines: [asyncTest]
+---*/
+
+function asyncTest(testFunc) {
+  if (!Object.hasOwn(globalThis, "$DONE")) {
+    throw new Test262Error("asyncTest called without async flag");
+  }
+  if (typeof testFunc !== "function") {
+    $DONE(new Test262Error("asyncTest called with non-function argument"));
+    return;
+  }
+  try {
+    testFunc().then(
+      function () {
+        $DONE();
+      },
+      function (error) {
+        $DONE(error);
+      }
+    );
+  } catch (syncError) {
+    $DONE(syncError);
+  }
+}
+
+assert.throwsAsync = async function (expectedErrorConstructor, func, message) {
+  var innerThenable;
+  if (message === undefined) {
+    message = "";
+  } else {
+    message += " ";
+  }
+  if (typeof func === "function") {
+    try {
+      innerThenable = func();
+      if (
+        innerThenable === null ||
+        typeof innerThenable !== "object" ||
+        typeof innerThenable.then !== "function"
+      ) {
+        message +=
+          "Expected to obtain an inner promise that would reject with a" +
+          expectedErrorConstructor.name +
+          " but result was not a thenable";
+        throw new Test262Error(message);
+      }
+    } catch (thrown) {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but an exception was thrown synchronously while obtaining the inner promise";
+      throw new Test262Error(message);
+    }
+  } else {
+    message +=
+      "assert.throwsAsync called with an argument that is not a function";
+    throw new Test262Error(message);
+  }
+
+  try {
+    return innerThenable.then(
+      function () {
+        message +=
+          "Expected a " +
+          expectedErrorConstructor.name +
+          " to be thrown asynchronously but no exception was thrown at all";
+        throw new Test262Error(message);
+      },
+      function (thrown) {
+        var expectedName, actualName;
+        if (typeof thrown !== "object" || thrown === null) {
+          message += "Thrown value was not an object!";
+          throw new Test262Error(message);
+        } else if (thrown.constructor !== expectedErrorConstructor) {
+          expectedName = expectedErrorConstructor.name;
+          actualName = thrown.constructor.name;
+          if (expectedName === actualName) {
+            message +=
+              "Expected a " +
+              expectedName +
+              " but got a different error constructor with the same name";
+          } else {
+            message +=
+              "Expected a " + expectedName + " but got a " + actualName;
+          }
+          throw new Test262Error(message);
+        }
+      }
+    );
+  } catch (thrown) {
+    if (typeof thrown !== "object" || thrown === null) {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but innerThenable synchronously threw a value that was not an object ";
+    } else {
+      message +=
+        "Expected a " +
+        expectedErrorConstructor.name +
+        " to be thrown asynchronously but a " +
+        thrown.constructor.name +
+        " was thrown synchronously";
+    }
+    throw new Test262Error(message);
+  }
+};
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/shell.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/shell.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/browser.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/browser.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/browser.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-done.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-done.js
new file mode 100644
index 0000000000..bab1bf956d
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-done.js
@@ -0,0 +1,70 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will reject promise if getter `done` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  ...
+  8. Let throwResult be Call(throw, syncIterator, « value »).
+  ...
+  11. Let throwDone be IteratorComplete(throwResult).
+  12. IfAbruptRejectPromise(throwDone, promiseCapability).
+  13. Let throwValue be IteratorValue(throwResult).
+  14. IfAbruptRejectPromise(throwValue, promiseCapability).
+  ...
+  20. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      throw() {
+        return {
+          get done() {
+            throw thrownError;
+          },
+          value: 1
+        };
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.throw().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-value.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-value.js
new file mode 100644
index 0000000000..9745df52c1
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-poisoned-value.js
@@ -0,0 +1,70 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will reject promise if getter `value` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  ...
+  8. Let throwResult be Call(throw, syncIterator, « value »).
+  ...
+  11. Let throwDone be IteratorComplete(throwResult).
+  12. IfAbruptRejectPromise(throwDone, promiseCapability).
+  13. Let throwValue be IteratorValue(throwResult).
+  14. IfAbruptRejectPromise(throwValue, promiseCapability).
+  ...
+  20. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      throw() {
+        return {
+          get value() {
+            throw thrownError;
+          },
+          done: false
+        };
+      }
+    }
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.throw().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-unwrap-promise.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-unwrap-promise.js
new file mode 100644
index 0000000000..9542254c75
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result-unwrap-promise.js
@@ -0,0 +1,66 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will unwrap a Promise value return by the sync iterator
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  ...
+  17. Let steps be the algorithm steps defined in Async-from-Sync Iterator Value Unwrap Functions.
+  ...
+  20. Return promiseCapability.[[Promise]].
+
+  Async-from-Sync Iterator Value Unwrap Functions
+  An async-from-sync iterator value unwrap function is an anonymous built-in
+  function that is used by methods of %AsyncFromSyncIteratorPrototype% when
+  processing the value field of an IteratorResult object, in order to wait for
+  its value if it is a promise and re-package the result in a new "unwrapped"
+  IteratorResult object. Each async iterator value unwrap function has a
+  [[Done]] internal slot.
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Don't catch me.")
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      throw() {
+        return {
+          value: Promise.resolve(42),
+          done: true
+        };
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  return yield* obj;
+}
+
+let iter = asyncg();
+
+iter.next().then(function (result) {
+  iter.throw(thrownError).then(
+    function (result) {
+      assert.sameValue(result.value, 42, "Result.value should be unwrapped, got: " + result.value);
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result.js
new file mode 100644
index 0000000000..90b02da8c2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/iterator-result.js
@@ -0,0 +1,60 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will call default sync throw
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  ...
+  8. Let throwResult be Call(throw, syncIterator, « value »)
+  9. IfAbruptRejectPromise(throwResult, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+  Generator.prototype.throw ( exception )
+  1. Let g be the this value.
+  2. Let C be Completion{[[Type]]: throw, [[Value]]: exception, [[Target]]: empty}.
+  3. Return ? GeneratorResumeAbrupt(g, C).
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.")
+
+function* g() {
+  yield 42;
+  throw new Test262Error('throw closes iter');
+  yield 43;
+}
+
+async function* asyncg() {
+  yield* g();
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  // throw will call sync generator prototype built-in function throw
+  iter.throw(thrownError).then(
+    function(result) {
+      throw new Test262Error('throw should cause rejection of promise');
+    },
+    function(err) {
+      assert.sameValue(err, thrownError, "promise should be reject with custom error, got: " + err)
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-get-throw.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-get-throw.js
new file mode 100644
index 0000000000..5a87c2e2ba
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-get-throw.js
@@ -0,0 +1,59 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will return rejected promise if getter of `throw` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.return ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "throw").
+  6. IfAbruptRejectPromise(throw, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      get throw() {
+        throw thrownError;
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.throw().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-throw.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-throw.js
new file mode 100644
index 0000000000..15656dbff8
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/poisoned-throw.js
@@ -0,0 +1,61 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will return rejected promise if getter of `throw` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  6. IfAbruptRejectPromise(throw, promiseCapability).
+  ...
+  8. Let throwResult be Call(throw, syncIterator, « value »).
+  9. IfAbruptRejectPromise(throwResult, promiseCapability).
+  ...
+  22. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Catch me.");
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      throw() {
+        throw thrownError;
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.throw().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, thrownError, "Promise should be rejected with thrown error");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+}).catch($DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/result-object-error.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/result-object-error.js
new file mode 100644
index 0000000000..f59d06cc8a
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/result-object-error.js
@@ -0,0 +1,65 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will return rejected promise if getter of `throw` abrupt completes
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let throw be GetMethod(syncIterator, "throw").
+  6. IfAbruptRejectPromise(thow, promiseCapability).
+  ...
+  8. Let throwResult be Call(throw, syncIterator, « value »).
+  ...
+  10. If Type(throwResult) is not Object,
+    a. Perform ! Call(promiseCapability.[[Reject]], undefined, « a TypeError exception »).
+    b. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var thrownError = new Error("Don't catch me.")
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      },
+      throw() {
+        return 1;
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+
+  iter.throw(thrownError).then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      let typeerror = err instanceof TypeError;
+      assert(typeerror, "Expect TypeError, got: " + err);
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);
+
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/shell.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/shell.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/shell.js
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-null.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-null.js
new file mode 100644
index 0000000000..9846e59b9a
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-null.js
@@ -0,0 +1,60 @@
+// |reftest| async
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: >
+  If syncIterator's "throw" method is `null`,
+  a Promise rejected with provided value is returned.
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+
+  [...]
+  5. Let throw be GetMethod(syncIterator, "throw").
+  [...]
+  7. If throw is undefined, then
+    a. Perform ! Call(promiseCapability.[[Reject]], undefined, « value »).
+    b. Return promiseCapability.[[Promise]].
+
+  GetMethod ( V, P )
+
+  [...]
+  2. Let func be ? GetV(V, P).
+  3. If func is either undefined or null, return undefined.
+flags: [async]
+features: [async-iteration]
+---*/
+
+var throwGets = 0;
+var syncIterator = {
+  [Symbol.iterator]() {
+    return this;
+  },
+  next() {
+    return {value: 1, done: false};
+  },
+  get throw() {
+    throwGets += 1;
+    return null;
+  },
+};
+
+async function* asyncGenerator() {
+  yield* syncIterator;
+}
+
+var asyncIterator = asyncGenerator();
+var thrownError = { name: "err" };
+
+asyncIterator.next().then(function() {
+  return asyncIterator.throw(thrownError);
+}).then(function(result) {
+  throw new Test262Error("Promise should be rejected, got: " + result.value);
+}, function(err) {
+  assert.sameValue(err, thrownError);
+  return asyncIterator.next().then(function(result) {
+    assert.sameValue(result.value, undefined);
+    assert.sameValue(result.done, true);
+  });
+}).then($DONE, $DONE);
diff --git a/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined.js b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined.js
new file mode 100644
index 0000000000..a2f6c4c65f
--- /dev/null
+++ b/js/src/tests/test262/built-ins/AsyncFromSyncIteratorPrototype/throw/throw-undefined.js
@@ -0,0 +1,54 @@
+// |reftest| async
+// Copyright (C) 2018 Valerie Young. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-%asyncfromsynciteratorprototype%.throw
+description: throw() will return rejected promise if sync `throw` undefined
+info: |
+  %AsyncFromSyncIteratorPrototype%.throw ( value )
+  ...
+  2. Let promiseCapability be ! NewPromiseCapability(%Promise%).
+  ...
+  5. Let return be GetMethod(syncIterator, "throw").
+  6. IfAbruptRejectPromise(throw, promiseCapability).
+  7. If throw is undefined, then
+    a. Perform ! Call(promiseCapability.[[Reject]], undefined, « value »).
+    b. Return promiseCapability.[[Promise]].
+
+flags: [async]
+features: [async-iteration]
+---*/
+
+var obj = {
+  [Symbol.iterator]() {
+    return {
+      next() {
+        return { value: 1, done: false };
+      }
+    };
+  }
+};
+
+async function* asyncg() {
+  yield* obj;
+}
+
+var iter = asyncg();
+
+iter.next().then(function(result) {
+  iter.throw().then(
+    function (result) {
+      throw new Test262Error("Promise should be rejected, got: " + result.value);
+    },
+    function (err) {
+      assert.sameValue(err, undefined, "Promise should be rejected with undefined");
+
+      iter.next().then(({ done, value }) => {
+        assert.sameValue(done, true, 'the iterator is completed');
+        assert.sameValue(value, undefined, 'value is undefined');
+      }).then($DONE, $DONE);
+    }
+  ).catch($DONE);
+
+}).catch($DONE);